Some embodiments of the invention relate to an aircraft seat attachment provided with a system for maintaining a clamping force by a spring effect. Some embodiments of the invention relate to an aircraft seat attachment provided with a system for locking an activation lever.
Aircraft passenger seats are generally mounted on a track 10, as shown in FIGS. 1a and 1b. The track 10 is a section having an upper lip 12 onto which the seat track fitting is clamped, this lip 12 being machined to enable insertion of the lower part of the attachment (studs) under the lip 12 of the track 10.
A seat is generally fixed to the track 10 by means of at least three attachments, typically four, two at the front of the seat and two at the rear. A passenger seat attachment 14, such as that shown in FIG. 2, must typically fulfill two principal functions, namely:                clamping the attachment 14 to the lip 12 of the track 10 to prevent any movement, and        for the rear attachments, transferring longitudinal loads, for example in the event of a crash, from the seat to the track 10.        
To this end, the attachment 14 comprises at least one stud 16 to be positioned under the lip 12 of the track 10. This stud 16 is either fixed relative to the attachment 14, in which case the attachment 14 includes a plunger 18 configured to vertically translate relative to a body 34 of the attachment (cf. FIG. 2), or the stud 16 is configured to vertically translate relative to the body 34 of the attachment 14.
To fix the seat to the track 10, the stud 16 enters a hole 20 in the track 10 and then moves longitudinally along the length of the track 10 by a half-pitch of the hole 20 to be located under the lip 12 of the track 10. The stud 16 is then moved vertically in order to come into contact with the lower face of the lip 12 and create a positive clamping action on the lip 12 of the track 10.
Two techniques are usually employed to generate the force clamping the attachment to the lip 12 of the track 10:                using a screw to move the stud 16 or the plunger 18 vertically; in this case, a hand tool is necessary and the clamping torque must be controlled in order to guarantee the clamping effect; this solution also enables infinite adjustment, making it possible to compensate for the tolerances of the parts used, or        using a system with no adjustments, possibly requiring the use of a hand tool, generally using a spring effect of a spring member 22 (spring washer, elastomer block, spring, etc.), enabling geometrical tolerances to be compensated and guaranteeing the required clamping.        
If necessary, longitudinal loads are transferred to the track 10 by a shear member 24 on a lower face of the plunger 18 accommodated in the holes in the track 10.
Systems with no adjustment generally employ an activation lever 26. In most cases, the lever 26 generates the clamping effect and the line B1 of the clamping force passes through the lever 26, as can be seen in FIG. 2. A locking system 28 is used to hold the lever 26 in place, situated for example at one end of the lever 26. This system 28 is formed by a hook 30, for example, adapted to cooperate with a stud 32 that is part of the body 34 when the lever 26 is in the locked position. However, some of these locking systems 28 do not sufficiently secure the seat to the track 10. In fact, the lever 26 and/or the locking system 28 often remains in an unstable locking position (cf. FIG. 3), wherein the lever 26 and/or the locking system 28 does not enable the energy peak corresponding to the clamping effect to be maintained in the event of stresses exerted on the attachment, such as vibration. In other systems, this locking position is not clearly identifiable.